add methods for Float16

base/float16.jl

@@ -157,7 +157,55 @@ for func in (:div,:fld,:cld,:rem,:mod,:atan2,:hypot)
 end
 
 ldexp(a::Float16, b::Integer) = float16(ldexp(float32(a), b))
-exponent(x::Float16) = exponent(float32(x))
+
+function exponent(x::Float16)
+    xu = reinterpret(UInt16,x)
+    k = int(xu >> 10) & 0x001f
+    if k == 0 # x is subnormal
+        xu == 0 && return x,0
+        axu = xu & 0x7fff
+        s = leading_zeros(axu)-4
+        axu <<= s
+        xu = (xu & 0x8000) | axu
+        k -= s
+    elseif k == 0x001f # NaN or Inf
+        return x,0
+    end
+    k - 15
+end
+function significand(x::Float16)
+    xu = reinterpret(UInt16,x)
+    k = int(xu >> 10) & 0x001f
+    if k == 0 # x is subnormal
+        xu == 0 && return x
+        axu = xu & 0x7fff
+        s = leading_zeros(axu)-4
+        axu <<= s
+        xu = (xu & 0x8000) | axu
+    elseif k == 0x001f # NaN or Inf
+        return x
+    end
+    xu = (xu & 0x83ff) | 0x3c00
+    reinterpret(Float16,xu)
+end
+function frexp(x::Float16)
+    xu = reinterpret(UInt16,x)
+    k = int(xu >> 10) & 0x001f
+    if k == 0 # x is subnormal
+        xu == 0 && return x,0
+        axu = xu & 0x7fff
+        s = leading_zeros(axu)-4
+        axu <<= s
+        xu = (xu & 0x8000) | axu
+        k -= s
+    elseif k == 0x001f # NaN or Inf
+        return x,0
+    end
+    k -= 14
+    xu = (xu & 0x83ff) | 0x3800
+    reinterpret(Float16,xu), k
+end
+
 ^(x::Float16, y::Integer) = float16(float32(x)^y)
 
 rationalize{T<:Integer}(::Type{T}, x::Float16; tol::Real=eps(x)) = rationalize(T, float32(x); tol=tol)